1. Field of the Invention
The present invention relates generally to missile tracking systems for tracking a target. More specifically, the present invention relates to a ball joint gimbal system for steering a gimballed mirror which is tracking a target.
2. Description of the Prior Art
A gimbal on a missile's seeker is used to establish a line of sight vector between a target and the missile's seeker. A visible or infrared sensor and associated optics are mounted on the gimbal. A narrow instantaneous field of view provides for long range tracking capability by the missile's seeker. The motion of the gimbal provides for a large angle of regard to accommodate the need for target acquisition which is off boresight. The image received by the seeker is stabilized in inertial space to decouple missile body motion which reduces blur. The gimbal is movable in elevation and azimuth so that closed loop tracking occurs. The angular rate of motion of the gimbal is measured to facilitate closed tracking.
Generally gimbals allow for orthogonal elevation and azimuth motion by including an inner gimbal platform, a gimbal ring and an outer gimbal fork. The inner gimbal platform has a number of components mounted thereon including an imager and its associated optical elements such as a mirror, lens or prism which provide the image. Rate or free gyros are mounted on the inner platform to provide inertial stabilization for the gimbal. A gimbal IR sensor has a cryogenic cooler.
A gimbal ring is attached to the inner gimbal platform on a shaft to allow for rotary motion of the gimbal. A torque motor and angle transducer are attached to this shaft. An orthogonal shaft attaches the gimbal ring to the outer gimbal fork. A second torque motor and associated angle transducer are attached to this orthogonal shaft. In addition, wires and cooling lines run across the gimbal axes. This causes a coupling between the axes so that body motion isolation is difficult to achieve.
The gimbal structure is complex and the mechanical components are very precise. The conventional gimbal is therefore very expensive and also large and heavy making it difficult to mount in the confined space of a seeker.
Accordingly, there is a need for a low cost, yet highly effective gimbal which is adapted for use with a missile's seeker.